How to Use a Cardboard Egg Container to Make a Seed Starting Tray
DIY Seed Starting Trays
A seed starting tray is a small container where you put garden soil or other materials used to germinate seeds so you can give plants proper care until it they are ready to be moved to the ground or a larger pot.
Because these trays are not big, it is easy to control their environment to help plants grow with the best conditions (watering, temperature, light, etc.). In geographic areas where winters are so cold that young plants cannot survive, you can start your seeds inside your house or other protected areas and be ready to transplant quite a few seedlings when the weather permits, instead of just starting everything from scratch.
There are several methods and materials you can use to make your own seed starting trays, but my favorite is the cardboard egg box.
Cardboard Box Preparation
Cardboard Egg Container Preparation
- Cut the lid and place it in the bottom: Cut the cover lid and place it in the bottom for support. Remember that you will be watering and cardboard softens with water.
- Make a hole for drainage: Some gardeners suggest making a little hole at the bottom of each egg compartment for draining. I don’t because puncturing the cardboard can make the bottom less resistant. When I water the tray, I am careful not to overdo.
- Fill each compartment with soil: I use a strainer to ensure that the soil is twig- and rock-free and that it will be uniform and compact. Also do not press the soil with your fingers or any other way.
- Water the tray: Do it slowly and/or by phases. Use only the just amount of water needed to get the soil moist. The first time you pour water, the earth may splatter, or water may linger on its surface without getting absorbed right away. As the soil absorbs more water, the earth will do a better job of filtering and absorption will be faster.
Cover With Plastic Bag
These seed starting trays may be very cozy for critters who may also eat your seedlings if you let them stay.
I dealed with a cockroach, and when I was transplanting I almost cut off the tail of an amazing blue-eyed brown-skinned gecko!
I wish I could show you an image, but both lizard (unharmed) and Hubber were too shocked for pictures!
Sowing Seeds in Your Seed Starting Tray
- Make little holes with your finger or a stick, as deep as necessary.
- Place the seeds in the holes and cover them with earth. Do not press, just cover.
- Water again slightly, until the earth is moist.
- Cover the cardboard tray with a transparent plastic bag to keep nice temperature and humidity. Use transparent plastic so you can see what's going on and to let light in. Note that using a plastic bag may not be necessary or can be even counterproductive in some climates – test it and see how the seeds germinate better.
- Place the seed starting tray on a ventilated and warm area. The top of the fridge is an all-time favorite, but be careful to chose a place where you are not likely to forget watering the tray.
- Once or twice a day, remove the plastic bag and let the tray breathe for a while.
- Water the seeds carefully every day. Use a glass to slowly pour water, or open the faucet and adjust it to a very limited flow before putting the seed tray beneath. If the jet of water is too strong, it can throw out the seeds (and spread dirt all over the place).
Each plant germinates according its own characteristics and specific conditions of its environment.So far, everything I have sown has germinated between 2 to 7 days.
If you notice several water drops inside the plastic bag (transpiration), it is due to overwatering or very warm and wet climate and you should adjust the water supply or even discard the use of the plastic bag.
As soon as your seedlings emerge, don't use the plastic bag anymore and continue watering every day, until they are strong enough to transplant them to the ground or a larger pot.
Your seedlings must have at least two sets of leaves before transplant.
Follow These Steps
Transplanting From the Tray to the Garden or Pot
What I love about these seed starting trays is the ease to transplant the plants. Make a hole a little deeper and wide enough to put the seedling roots inside. When you set the plant, it should have enough space to fit its roots comfortably and it should be set deeper than it is in the tray.
Use scissors to cut each egg carton compartment.
You do not have to transplant all your seedlings at the same time and you can use the same seed starting tray to sow several type of plants, especially if you set them in germination order.
You can transplant the complete tray carton base to the soil (watering would end incorporating the cardboard to the soil), but I thought I should help the roots a little by removing the bottom and it is really easy to do when the cardboard is wet.
I also removed the whole thing from other seedlings (I wanted to test both approaches). An advantage of using strained soil is that it becomes evenly compacted around the roots with each watering and it is very easy to cut or peel wet cardboard get a nice root ball.
Plants free from cardboard grew faster. You can see in the big picture below the difference in sizes. When I realized this, I removed the cardboard from the little one and replanted. However, all plants were healthy. Maybe if I had left the small one alone, it would eventually grew as big as the others, only slower.
After using a seed starting tray for the first time, I thought it may not be necessary at all because I live in a nice, warm place. So, in my next gardening project I sowed more seeds directly in pots. The seeds germinated but not as fast (being the same plant).
The explanation is that when you water a pot, the water eventually drains to the bottom, and since your seeds are in the top, you will have to use a lot of water every day to keep the earth around them moist. A lot of water is wasted!
It’s also easier and faster to water several seedlings in small trays that are close together, than seedlings in different pots that require abundant but careful watering.
That is another good reason to use these trays.
Transplanting Without Cardboard vs. With Cardboard
There are several commercial brands that sell starting trays and containers, but using cardboard egg boxes is a nice and easy way to save some money and reuse something instead of throwing it away.
Also, keep in mind that everything I applied here may be done in several other ways. Feel free to experiment and share your results.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.